The present invention relates to the field of medical diagnosis, and provides a system and method for computerized modeling of the human spinal cord, for purposes of predicting the likelihood of spinal cord damage.
The invention provides a model of the central nervous system that is based on clinical data (e.g. neurological examination), circumstantial data (e.g., mechanism of injury, and injury-specific data, such as vehicle speed and angle of impact force vector with respect to the patient), and anatomical data (e.g., MRI, CT, Myelogram-CT, radiographs in flexion and extension, etc.). The invention produces a mathematical model that comprises a three-dimensional stress/strain image of the central nervous system. The model of the present invention also can provide a hypothesized finite element rendering of the central nervous system at the time of impact. The program can also predict the probability of neurological damage.
For many years, neurosurgeons, orthopedic spinal surgeons, and neuroscientists have grappled with the problems associated with spinal cord injury. Spinal cord injury is a major consequence of motor vehicle accidents, diving accidents, and sporting accidents. Well publicized examples of quadriplegia resulting from football accidents, for example, have drawn attention to the need for predicting when an individual is susceptible to, or at high risk for, a significant spinal cord injury.
Such predictions have been made, in the prior art, on the basis of static images derived from myelography, computerized tomography, and magnetic resonance imaging. Such imaging techniques, however, rely on interpretation of the anatomy of the patient in a neutral position, within the context of known standards, to make an assessment as to risk category. For instance, a football player with narrowing of the cervical spinal canal is considered at significantly greater risk than a football player with no narrowing of the spinal canal.
The presence of narrowing, in the above example, however, takes into account only the cross-sectional area of the spinal canal and the relative forces of compression placed on the spinal cord. Hitherto, neuroscientists and spine surgeons working with the spinal cord have placed excessive and perhaps undeserved importance on the presence of compression and consequent ischemia of the spinal cord. Proposed risk analysis strategies, therefore, have been suggested on the basis of compression and on the assumption that compression causes spinal cord injury via ischemia.
These assumptions, however, may be incorrect. New paradigms with animal models have demonstrated the importance of stretch and shear in neural injury. Other clinical studies suggest that spinal cord injury may largely be the result of the abnormal stretch and shear forces imparted to the spinal cord during excessive flexion, extension and lateral bending injuries. The importance of stretch and shear to chronic, non-traumatic injuries of the central nervous system seems pertinent.
While studies that model spinal stretch and shear can be performed in animals, they obviously cannot be demonstrated in humans. It is therefore desirable to develop a mathematical model of the spinal cord, and to apply an elemental analysis of the stresses applied, by an external load, to each biomechanically distinct region or tract of the spinal cord, and to measure the resulting strains. A computer simulation program can thus determine predicted loading patterns and stresses within the human spinal cord.
Spinal cord injuries often defy diagnosis. A patient may report symptoms such as pain, neurologic deficits, blurred vision, lack of hand coordination, change in gait, etc., yet the standard images formed by MRI scanners or the like may show nothing. The patient's strength and sensations may appear to be satisfactory, yet the patient is still suffering. The present invention is based, in part, on the hypothesis that many such injuries result from stretching or compression of the spinal cord, and that such stretching or compression is not readily observed by conventional means.
The present invention therefore provides a model of the spinal cord, and provides a method of simulating the loading patterns and strains within the spinal cord, so as to correlate certain patterns of strains with various kinds of central nervous system injury. The invention comprises, in part, a heuristic program which allows the model to develop information based on a database of accumulated clinical observations.